Peripheral vascular disease (2%) and carotid bruit (1%) were similar to other studies.11,17 Polycythemia, a known risk factor for stroke at altitude, was present ...
Original Article
Stroke at Moderate Altitude SK Mahajan*, R Kashyap*, BR Sood*, P Jaret*, J Mokta #, NK Kaushik**, BS Prashar##
Abstract Objective : To know the clinical profile, presence of various risk factors for stroke at moderate altitude and to study its relationship with hypertension and polycythemia at moderate altitude. Methods : We analyzed the data of 100 patients, consecutively admitted to a hospital situated at an moderate altitude of 2200 meters MSL of Sub-Himalayan ranges and studied the age, gender, geographical distribution, clinical features and presence of various risk factors in relation to stroke. This is not only the first study conducted in Himachal Pradesh but also first study in India to be conducted at moderate altitude (2000-3000 meters MSL). Results : Males outnumbered females (66% males, 34% females) with rural predominance (73% rural, 27% urban). Cerebral infarction (69%) was more common but primary intracerebral haemorrhage (26%) was more common than found in the West. Hypertension (62%) and smoking (60%) were most common risk factors present and polycythemia was not a significant risk factor at this altitude. Conclusion : Incidence of stroke was found to be lower than the study conducted at low altitude. Incidence of various types of stroke was similar to other Indian studies. The combination of opposite effects of decreased hypertension and increased haematocrit could not be demonstrated at this altitude and smoking was more common than in other studies and other risk factors prevalent were same as that for low altitude. ©
INTRODUCTION
H
imachal Pradesh is situated in north-west of India and is mainly a hill state and has inhabited areas ranging from 600 - 4000 meters mean sea level. No data is available regarding incidence and pattern of various risk factors prevalent from this area. Although it is hypothesized that there is low prevalence of stroke at high altitude but the role of altitude in stroke has not been established; however some studies report a possible relationship between altitude and stroke with a lower prevalence of stroke at higher altitude. 1,2,3 Few epidemiological surveys conducted at different altitude suggest that cerebrovascular disease (CVD) may be less frequent than at sea level. Many areas of USA with low stroke death rates are located at higher altitude while highest rates are along the sea coast.1 The blood pressure (BP) decreases and may reach a plateau above 3000 meters with low mean values of systolic and diastolic BP. The fall in systolic BP is greater than diastolic. The patient with systemic hypertension showed amelioration
*Registrar, #Assistant Professor, ##Professor and unit Head, Department of Medicine; ** Professor and Head, Department of Radio Diagnosis; IG Medical College Shimla H.P. India, Pin- 171001. Received : 14.11.2003; Revised : 7.4.2004; Accepted : 28.7.2004
© JAPI • VOL. 52 • SEPTEMBER 2004
in their level of systolic BP. 4,5 The heamatocrit and haemoglobin levels increase exponentially with altitude. At high altitude there is a definite increase in red cell volume thus increase in total blood volume but plasma volume is reduced. With increasing altitude, the absolute quantity of oxygen carried by blood increases owing to rising haemoglobin concentration thus heightening the viscosity of blood. 6,7 The Framingham Study 7 showed that high haemoglobin was a risk factor for cerebral infarction (CI). It was also found that men with Hb > 15 gm % and women with Hb > 14 gm % had twice as many CIs as their cohort with normal haemoglobin. As hypertension and polycythemia are well known risk factors for CVD. The combination of opposite effects of the decrease in BP and increase in heamatocrit led to the hypothesis of a relationship between altitude and stroke and this relationship may vary in relation to different altitude.8
MATERIAL AND METHODS This study was conducted in a tertiary care hospital situated at a moderate altitude of 2200 meters mean sea level (MSL). This is not only the first study conducted in Himachal Pradesh at an altitude of 2200 meters but also first study in India to be conducted at moderate altitude (2000-3000 meters MSL). One hundred and eight consecutively admitted patients with clinical diagnosis of stroke were taken and patients with
www.japi.org
699
neurological deficit caused by non-vascular causes like tumour, tuberculoma, trauma etc. were not included in this study. So, 100 patients, all natives of this area, were included in this study. Detailed history was taken noting age, gender, social and geographic distribution along with various risk factors. Patients aged up to 45 years were defined as stroke in young. Complete clinical examination including neurological examination was done. Hypertension was diagnosed as per JNC VI criteria. Hb ≥ 15 gm % in male and ≥ 14 gm % in female was defined as polycythemia. In all cases diagnosis, type of stroke along with site of lesion was confirmed with CT scan brain (plain) and if required contrast studies were also done. Biochemical investigations like random blood sugar, and if required fasting blood sugar, renal function tests, ECG, urine routine examination were done in all the cases. Special investigations like echocardiography were also done when indicated. Statistical evaluation was done from the data collected. p value < 0.05 was taken as significant. r, correlation co-efficient between variables was also calculated. z value was calculated where number of variables was less than 30 (stroke in young) and value of >1.96 was taken as significant.
RESULTS One hundred cases of stroke in the study were aged 20 to 85 years, average age 57.88 years (M 55.65 yrs, F 52.29 yrs). The maximum number of cases was in 6th and 7th decade. 66 (66%) were males and 34 (34%) were females, M: F 1.95:1 which decreased to 1.26:1 in stroke in elderly (>65 yrs). Majority (73%) was from rural areas and 27% belonged to urban background. Incidence of stroke in young was 20%. On CT scan 96 (96%) were anterior circulation strokes, 3% posterior circulation strokes and 1% subarachnoid haemorrhage (SAH). Lesions on left side of brain were more common (57L, 32R, 10 B/L and 1 SAH). On CT scan brain 69 (69%) had cerebral infarction (CI), 26 (26%) had primary intracerebral haemorrhage (PICH), 4% had both types of lesions and remaining 1% had SAH. Parietal lobe (50%) was most commonly involved site, extensive lesions (≥ 2 areas involved) in 41% was next most common. Cerebellum (3%), temporal (3%) and frontal (2%) were other areas involved. Eighty three (83%) percent had hemiparesis and monoparesis was present in 2%. Hemiparesis, seventh nerve palsy and speech disorders were equally distributed among CI and PICH, whereas headache vomiting and altered sensorium more common in PICH. Distribution of clinical features is given in Table 2. Table 1: Distribution of cases according to age Age in Years 20 30 40 50 60 70 80
-
700
29 39 49 59 69 79 89
Number of patients 3 9 16 22 26 15 9
Presence of various risk factors along with their relationship and significance with various types of stroke is given in Tables 3 and 4. Hypertension was present in 62% and was most significant (p-0.0217) risk factor. The presence of hypertension at the time of examination was more significant (p-0.0452) than past history of suffering from hypertension (p-0.0710). Mean values of systolic and diastolic BP were higher in males than females (184/ 108 vs 163/ 96 mm of Hg). The mean BP recorded in PICH (160.6/ 99.5 mm of Hg) was higher than in CI (146.6/ 89.6 mm of Hg). Association of hypertension was more significant with PICH (p-0.0215) than CI (p-0.0341). However, both types were significantly associated with hypertension. Smoking was another significant risk factor associated with stroke (p0.0301) and association with CI (p-0.0371) was more significant than PICH (p-0.0398). Polycythemia was noted in 2%, 68% of our patients had Hb 14 gm%. Both hypertension and smoking were present in 36%, hypertension smoking and diabetes mellitus (DM) in 6%, hypertension and heart disease in 3%, hypertension and DM in 2%, smoking and heart disease in 2%, smoking and DM in 1%. In this study risk Table 2 : Distribution of clinical features in different types of stroke Clinical features
Stroke (n=100)
Cerebral infarction (n=69)
Intracerebral Subarachnoid hemorrhage hemorrhage (n=26) (n=1)
Hemiparesis 7th N palsy Speech disorders Altered sensorium Headache Vomiting Seizures
83 (83%) 74 (74%) 46 (46%)
58(84%) 51 (73.9%) 34 (49.2%)
21 (80.7%) 19 (73%) 11 (42.3%)
0 0 0
28 (28%)
16 (23.1%)
10 (38.4%)
1
15 (15%) 8 (8%) 6 (6%)
5 (7.2%) 2 (2.8%) 5 (7.2%)
9 (34.6%) 5 (19.2%) 1 (3.8%)
1 1 0
Table 3 : Distribution of risk factors in different types of stroke Risk factor
Stroke (n=100)
Cerebral infarction (n=69)
Hypertension Smoking Past h/o stroke/ TIA Diabetes mellitus RHD AF IHD PVD Polycythemia Carotid bruit Postoperative state Rheumatiod arthritis
62 (62%) 60 (60%) 10 (10%)
38 (55%) 21 (80.7%) 44 (63.7%) 14 (53.8%) 9 (13%) 1 (3.8%)
1 0 0
9 (9%)
8 (11.5%)
0
0
6 6 3 2 2 1 1
6 6 3 2 2 1 1
(8.6%) (8.6%) (4.3%) (2.8%) (2.8%) (1.4%) (1.4%)
0 0 0 0 0 0 0
0 0 0 0 0 0 0
1 (1.4%)
0
0
www.japi.org
(6%) (6%) (3%) (2%) (2%) (1%) (1%)
1 (1%)
Intracerebral Subarachnoid hemorrhage hemorrhage (n=26) (n=1)
© JAPI • VOL. 52 • SEPTEMBER 2004
Table 4: Relationship of main risk factors with types of stroke Type of stroke Stroke Cerebral infarction Intracerebral hemorrhage Stroke in young Cerebral infarction in young Intracerebral hemorrhage in young
r p r p r p r z r z r z
Hypertension
Hypertension at admission
Hypertension past history
Smoking
Diabetes mellitus
0.6981 0.0217 0.6992 0.0341 0.7629 0.0215 0.6981 1.12 0.5610 2.18 0.4780 0.96
0.5905 0.0452 0.6528 0.0423 0.7629 0.0215 — — — — — —
0.3908 0.0710 0.6201 0.0475 0.4618 0.0710 — — — — — —
0.7108 0.0301 0.7820 0.0371 0.5628 0.0398 0.6627 2.82 0.6819 2.58 0.3571 1.56
0.2156 0.1272 0.3125 0.1050 — — — — — — — —
r = correlation coefficient; p = p value; p < 0.05 - Significant; z = z value; z > 1.96 - Significant; 1.00 - perfect correlation; 0.90 - very strong correlation; 0.70-0.80 - strong correlation; 0.50-0.60 - Moderate correlation; 0.40 or less - Weak correlation
factors could be identified in 91% cases. Following diseases were found to be associated with stroke in the study, chronic obstructive pulmonary disease in 24%, senile cataract in 3%, and pulmonary tuberculosis in 2%, pleural effusion in 2%, myasthenia gravis, cholelithiasis and tubercular meningitis in 1% each.
DISCUSSION In our study stroke formed 0.9% of total admissions to the hospital and 3.3% of all admissions in the medical wards during the period of study. Dalal PM9 analyzed data from major university hospitals in India from low altitude, found 2% of total hospital admission and 4.5% of admission to medical wards were due to stroke. Thus incidence of stroke was less at moderate altitude than at low altitude and was found consistent with concept of decreased incidence of stroke with increasing altitude.1,2,3 Cerebral infarction was predominant lesion and relative high incidence of PICH in comparison to the West was found and it was consistent with other studies.10,11 The rural predominance in this study may be because of the fact that most of the patients attending to our hospital are from rural background. The incidence of stroke increased with age which was similar to that found by Maria AK et al.12 The male preponderance and higher incidence of hypertension was comparable with other studies.2,13,14 The higher association of hypertension with PICH (80.7%) than in CI (57.5%) was comparable with a study conducted in AIIMS.15 The higher incidence of smoking in our study may be because of the fact that 26% of females in the study were found to be smokers. Past history of stroke/ TIA was comparable with Kaur K et al.16 Prevalence of DM in our study was similar to three studies including one done in Kashmir valley.12,13,14 Incidence of rheumatic heart disease (6%) was also similar to other studies done in the northern region.2,16,17 Incidence of coronary artery disease (3%) in patients with stroke was lower than at low altitude12,15 but was similar to its incidence at high altitude.1 Only one-third of patients in the study were aged more than 65 years, the age group with maximum incidence of atrial © JAPI • VOL. 52 • SEPTEMBER 2004
fibrillation might have contributed to the lower incidence of AF. Peripheral vascular disease (2%) and carotid bruit (1%) were similar to other studies.11,17 Polycythemia, a known risk factor for stroke at altitude, was present only in 2%. Because of various grades of nutritional deficiencies in Indians, they achieve low mean haemoglobin.18 This fact is well reflected by the fact that 68% of patients in the study had Hb
